One more suggestion is to use "retired" commercial equipment. IMO it will outperform all of the brand new HAM repeaters for a whole lot less money. All of my repeaters are GE Mastr II's. The 100 watt continuous duty models can be had for around $200. It takes a bit of knowledge to get them up and running on the ham bands, but they do not have to be modified - just retuned.
I agree some of the commercial stuff is the way to go, I personally have 3 Master II repeaters up, they just keep ticking. With one caveat, get the older style control racks, with the separate control cards. Back in the late 80s early 90s GE came out with the new and improved master II with the all in one control board made by IDA corp.... If you find one of those get it for free, then spend some time ditching the IDA board and installing a real controller. If you have to give more than $.01 for it run away.
As far as Antennas/Duplexers I agree with most of the comments that it is just plain easier and more cost effective to put in a good set of cans. Another point is get a good antenna, dont do what a lot of hams do when they go by a commercial shop and pick up our take downs... There is a reason we took them down, and most are cut for another freq and will not tune well at all in the ham band, the one notable exception is some of the folded dipoles that are wide band (like from 138-174mhz). Again if they are laying against the side of a shop there is a reason, sometimes you can get lucky though and pick up one that you can rebuild cheaply.
Also dont go buy a diamond antenna and expect it to last more than a few months to a year up on a mountain.
Have fun. If you need a set of good cans let me know, I have 5 sets sitting out in the shop that I would part with.